package day_2022_4_to_7.day48;

import java.util.Scanner;

/**
 * @author haomin
 * @date 2022/06/02 17:48
 **/
public class Day34_2_FibRabbit {
    public static void main(String[] args){
        Scanner in = new Scanner(System.in);
        while(in.hasNext()){
            int n = in.nextInt();
            long[] dp = new long[n+1];
            dp[1] = 1;
            dp[2] = 2;
            for(int i = 3; i <= n;i++){
                dp[i] = dp[i-1] + dp[i-2];
            }
            System.out.println(dp[n]);
        }
    }
}